In fluid valve assemblies, a rotating or sliding operating member, such as a valve stem normally includes a valve plug on the end thereof for engagement with the valve seat in controlling the flow of fluid through the valve. During assembly, a metal valve plug formed with a threadable member is threadably engaged with the valve stem until the plug is securely threadably tightened onto the stem.
In certain situations, it is desired to utilize non-metal material, such as ceramic for the valve plug. First of all, it is very difficult and expensive to incorporate threads on ceramic material, either on the exterior or interior of a ceramic valve plug. Secondly, even when this is accomplished, the normal type of threadable attachment of a valve plug with a valve stem often leads to cracks in the ceramic plug due to the differences in material characteristics and properties between the ceramic plug and the threadably engaged metal stem.
Accordingly, it is desired to provide apparatus and a method for reliably attaching a non-metal part, such as a ceramic plug to a metal valve stem in a reliable, easy, and inexpensive manner.